The present technology relates to non-volatile memory.
Recently, ultra high density storage devices have been proposed using a 3D stacked memory structure sometimes referred to as a bit cost scalable (BiCS) architecture. For example, a 3D NAND stackable memory device can be formed from an array of alternating conductive and dielectric layers. A memory hole is drilled in the layers to define many memory layers simultaneously. A NAND string is then formed by filling the memory hole with appropriate materials. A straight NAND string extends in one memory hole, while a pipe- or U-shaped NAND string (P-BiCS) includes a pair of vertical columns of memory cells which extend in two memory holes and which are joined by a bottom back gate. Control gates of the memory cells are provided by the conductive layers.
However, there is a continuing need to reduce the size of such memory devices.